The mechanical properties and histology of adult femoral bone from men and women will be investigated to determine if there are statistically significant differences. A second project is a study of the mechanical properties and biomechanical behavior of the epiphyseal plate in long bones of children and how they change with age. This study should provide information on the mechanics of epiphyseal plate trauma in children. A similar investigation will be made with bones of puppies of known age. A third project is an investigation of the mechanical properties and histology of long bones of commonly used experimental animals. Data obtained from these animals is often extrapolated to human bone although the mechanical properties and histology of the experimental animal bone may be different from those of human bone. The proposed study should reveal these differences and provide data on which experimental animal bone can best be used as a model for human bone.